MODIFICATION OF COI.OR. 



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T«XT-FiGURE 13.— To illustrate the results obtained in a series of experiments of which two (14 and 15 

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Text-figure 14.— To illustrate the results that were obtained in a series of experiments as described 

 in the text when continued for a number of generations. Each of the dififerent lines represents a 

 series of experiments and the arrow heads the direction taken by different parts of each set when 

 the stimulus was removed or applied. In all the sets of experiments represented lines going toward 

 the modal line of the parents indicate the rapid return of the beetles to the modal condition when 

 the stimulus was removed. 



